Roller cam rocker arm question

[clutterhead]

Hello,

I am swapping an L31 roller cam into a flat tappet TBI. I have everything to do the swap. Cam, retainer plates/ lifter brackets, lifters, pushrods, and springs with spring retainers from a roller cam block. I have a question about the stock rocker arms though. I am finding conflicting info on if the stock flat tappet rockers are ok to use. I've read that they are, but then I came across a video of someone doing the swap. The only difference is he is swapping the smog heads to vortec heads, which I am not doing. In the video, he explains that the rocker arms also need to be replaced when doing the roller cam swap because they have slots where the rocker contacts the valve that prevent the pushrod from allowing the rocker to have side to side play when the engine is running. The reason he says this happens is that the pushrods have no guides in the heads as they would in a stock flat tappet setup. I'm confused because my heads don't have guides either. Just a hole in the stock smog heads that go down into the lifter. When I look up the difference in stock rocker arms for a roller cam engine they indeed are different. Yet I find people saying you can use the old rockers from the flat tappet cam. Which is correct?

The video for reference. About 2 mins in:
Video

Thanks

 

[pressureangle]

The holes in your stock smog heads are actually slots and act as pushrod guides. They are problematic with cam and rocker swaps; they usually constrain the pushrod's range of motion with any increased lift. I swapped a set of 'true ratio' 1.55/1.60 ratio roller tip rocker arms on my otherwise stock '94 5.7, and the pushrods rubbed enough on the ends of the head slots I'd not have sold it to a customer, although it went 30k after that before getting shelved. So be prepared, you can use the stock rockers with a cam that came stock in some vehicle underneath these heads, but you may have a CTJM with other than stock rockers. But you don't need pushrod guides.

 

[clutterhead]

The holes in your stock smog heads are actually slots and act as pushrod guides. They are problematic with cam and rocker swaps; they usually constrain the pushrod's range of motion with any increased lift. I swapped a set of 'true ratio' 1.55/1.60 ratio roller tip rocker arms on my otherwise stock '94 5.7, and the pushrods rubbed enough on the ends of the head slots I'd not have sold it to a customer, although it went 30k after that before getting shelved. So be prepared, you can use the stock rockers with a cam that came stock in some vehicle underneath these heads, but you may have a CTJM with other than stock rockers. But you don't need pushrod guides.

Thanks for the reply.

I'll keep a lookout for the pushrods rubbing. I think I'll pick up the stock L31 rocker arms to give it the best shot it has at working out. Couldn't hurt

 

[Supercharged111]

Thanks for the reply.

I'll keep a lookout for the pushrods rubbing. I think I'll pick up the stock L31 rocker arms to give it the best shot it has at working out. Couldn't hurt

L31s are self aligning. I once heard from an engine builder you're not supposed to combine a guide plate with a self aligning rocker. I realize you don't have plates, but kinda the same idea here.

 

[clutterhead]

L31s are self aligning. I once heard from an engine builder you're not supposed to combine a guide plate with a self aligning rocker. I realize you don't have plates, but kinda the same idea here.

Thanks for pointing that out. This is why I'm doing all stock. Not experienced enough with mods to want to mess around too much haha. Just replacing the flat tappet cam because of a bad lifter so I'm ok with all stock roller parts to get a daily running again.

 

[Schurkey]

LOOK at your existing rocker arms.

They're probably self-guiding just like the Vortec L31 rockers.

Do not use self-guiding rocker arms, AND guided pushrods--either with guideplates, or slotted holes in the cast-iron heads that guide the pushrods. (ROUND holes in the heads don't guide pushrods.)

Just as important--make sure the rocker arms aren't worn-out at the pushrod socket, the pivot and pivot ball, and--most common--at the valve tip.